Infectious agents, parasitic diseases or cellular pathologies are becoming more resistant to conventional methods of protection or treatment. These methods include vaccines, antibiotics, or immuno-modulating drugs. In controlling disease, one field that is gaining momentum is the development of compounds that stimulate the body""s natural defences. These natural defences have been simplified as being of two responses: humoral immunity and cell mediated immunity.
Humoral, or specific, immunity involves the production of specific antibodies in an infected animal as a result of the presence of an invading microorganism or toxin having a particular antigen. These antibodies either congeal or inactivate the invader, or interact with other blood components, such as complement (a system of plasma proteins that interact with antibodies), to destroy it.
Cell mediated (cellular) immunity involves, in part, the activation of phagocytic cells in the host animal to become metabolically more active and digest or chemically neutralize invading foreign objects.
There are difficulties in stimulating either of these defences. In the case of humoral immunity: it requires several months of immunization to develop a response; antibody levels resulting from this form of immunity diminishes over several months; not all vaccines are effective in triggering an immune response (e.g. susceptibility to Dengue Fever actually increases with experimental vaccination); humoral immunity is useless against parasitic diseases (which invade the cells and are protected from antibodies or drugs); and, it is very specific to the serotype of a given microbe.
With cell meditated immunity, xe2x80x9cimmuno-modulatorsxe2x80x9d, or drugs that stimulate activity, enhance cellular activity either poorly or with little effect. Further, these compounds are frequently toxic (resulting in nausea, fevers, malaise and death), and may have unwelcome side effects on the activity of other cell sub-populations. Examples of such immuno-modulators are nucleic acid analogues, chemically defined drugs, adjuvants and biologically active peptides. These drugs are useful for only certain diseases.
One group of immuno-modulators that appears to have become overshadowed by other modulators are glycans which are carbohydrates extracted from micro-organisms, especially plants and yeast (Seljelid et al, 1981, xe2x80x9cGlycan Stimulation of Macrophages in vitroxe2x80x9d, Exp. Cell. Res. 131:121-129). Glycans are also referred to as glucans, but in this report the term glucans will be used to refer to polymers of glucose. Seljelid et al (1981) found that xe2x80x9conly insoluble glycans are effective in stimulating macrophagesxe2x80x9d and, of these glycans, the presence of 1,3-beta linkages of the sugars was believed to be a contributing factor.
D""Hinterland et al in U.S. Pat. No. 4,734,403 (issued Mar. 29, 1988) isolated a membrane polysaccharide from bacteria which was found to have an immuno-modulating effect on natural killer cells to destroy Maloney""s lymphoma. The polysaccharide taught in this patent comprises a chain of galactofuranose and galactopyranose units and is isolated from gram negative bacteria. In U.S. Pat. Nos. 4,933,440 and 4,937,327, d""Hinterland et al teach immuno-modulators derived from the bacterial polysaccharides recited in the 4,734,403 patent.
The polysaccharide noted by d""Hinterland et al is extracted by cellular disruption, alkaline digestion and dissolving in water; it is unknown whether this polysaccharide can protect against its source bacterium, Klebsiellapneumoniae. As most immuno-modulators act only for a few days, this may be why the in vivo trials disclosed in the d""Hinderland references were conducted at most 3 days after immunization. The polysaccharide had adjuvant properties for enhancing antibodies (i.e. humoral immunity not cellular immunity) when it was given at the same time as a ribosomal vaccine. These publications are encouraging for other researchers, not only because of the anti-cancer properties of d""Hinderland""s discovery, but also because of their findings that bacterial polysaccharides may have immunological effects.
In contrast, the present inventors have discovered that the O-polysaccharide (OPS) of Brucella used previously to either differentiate infected from vaccinated cattle (Cherwonogrodzky et al., U.S. Pat. No. 5,006,463) or to protect animals from brucellosis (Cherwonogrodzky et al., Canadian application 2,164,155), has immunomodulating properties. Although this polysaccharide is associated with the cell membrane when bound to lipopolysaccharide or LPS, in strain B. melitensis B 155 it is found loose in the periplasmic space, in B. melitensis 16M it is shed into the medium, and there is still controversy if it can form a capsule or form xe2x80x9cnative haptenxe2x80x9d which is secreted away from the cell. Also, another polysaccharide associated with Brucella but not found in many other bacteria, referred to herein as xe2x80x9cpoly Bxe2x80x9d, has similar immunomodulating effects in that it can also greatly increase the activity of macrophages as evidenced by chemilumenescence. These polysaccharides differ in composition, structure and sometimes location to the polysaccharide noted by d""Hinterland and these are purified by different methods. These polysaccharides (there is more known about the OPS) appear to have some different properties compared to the one presented by d""Hinterland.
Accordingly, in one embodiment, the present invention provides an immuno-modulating compound comprising an effective, non-toxic quantity of bacterial polysaccharide for enhancing cell mediated immunity in an animal against bacteria, fungi, yeast, viruses, parasites and cellular abnormalities.
The polysaccharides of the invention comprise bacterial OPS and Poly B molecules and polysaccharides cross reactive therewith and mixtures thereof.
Further, the invention provides for the use of such polysaccharides in the treatment and prevention of various infections as well as the treatment of carcinomas and other cellular pathologies.